A proposed power output apparatus is mounted on a hybrid vehicle equipped with a motor generator and an engine, which is drivable with a variation in supply rate of exhaust gas to an intake pipe (EGR rate or exhaust gas recirculation rate) (see, for example, Japanese Patent Laid-Open Gazette No. 2000-282910). This prior art power output apparatus drives the engine with a target EGR rate, which is set according to the measurements of an engine rotation speed, a fuel injection flow, and a cooling water temperature of the engine. Such control is expected to ensure a certain level of emission control performance and minimize the emission of toxic components (NOx).